No Arabic abstract
The simplest little Higgs model predicts a light pseudoscalar boson $eta$ and opens up some new decay modes for $Z$-boson, such as $Z to bar{f} f eta$, $Zto etaetaeta$, $Zto etagamma$ and $Zto eta gg$. We examine these decay modes in the parameter space allowed by current experiments, and find that the branching ratios can reach $10^{-7}$ for $Zto bar{b}beta$, $10^{-8}$ for $Zto bar{tau}taueta$, and $10^{-8}$ for $Zto etagamma$, which should be accessible at the GigaZ option of the ILC. However, the branching ratios can reach $10^{-12}$ for $Zto etaetaeta$, and $10^{-11}$ for $Zto eta gg$, which are hardly accessible at the GigaZ option.
In the framework of the simplest little Higgs model (SLHM), we study the production of a pair of neutral CP-even Higgs bosons at the LHC. First, we examine the production rate and find that it can be significantly larger than the SM prediction. Then we investigate the decays of the Higgs-pair and find that for a low Higgs mass their dominant decay mode is hh->etaetaetaeta (eta is a CP-odd scalar) while hh->bbar{b}etaeta and hh->etaeta WW may also have sizable ratios. Finally, we comparatively study the rates of pp-> hh -> bbar{b}tau^+ tau^-, pp->hh->bbar{b}gammagamma, and pp->hh->WWWW in the SLHM and the littlest Higgs models (LHT). We find that for a light Higgs, compared with the SM predictions, all the three rates can be sizably enhanced in the LHT but severely suppressed in the SLHM; while for an intermediately heavy Higgs, both the LHT and SLHM can enhance sizably the SM predictions.
We analyse the consequences of the little Higgs model for double Higgs boson production at the LHC and for the partial decay width of the Higgs into two photons. In particular, we study the sensitivity of these processes in terms of the parameters of the model. We find that the little Higgs model contributions are proportional to (v/f)^4 and hence do not change significantly either single or double Higgs production at hadron colliders or the partial decay width of the Higgs into two photons as compared to the standard model predictions. However, when interference and mixing effects are properly taken into account these contributions increase to be of the order of (v/f)^2.
In the simplest little Higgs model the new flavor-changing interactions between heavy neutrinos and the Standard Model leptons can generate contributions to some lepton flavor violating decays of $Z$-boson at one-loop level, such as $Z to tau^{pm}mu^{mp}$, $Zto tau^{pm}e^{mp}$, and $Z to mu^{pm}e^{mp}$. We examine the decay modes, and find that the branching ratios can reach $10^{-7}$ for the three decays, which should be accessible at the Giga$Z$ option of the ILC.
We study Lepton Flavour Violating hadron decays of the tau lepton within the Simplest Little Higgs model. Namely we consider $tau rightarrow mu (P, V, PP)$ where $P$ and $V$ are short for a pseudoscalar and a vector meson. We find that, in the most positive scenarios, branching ratios for these processes are predicted to be, at least, four orders of magnitude smaller than present experimental bounds.
The Littlest Higgs Model with T-parity is one of the attractive candidates of physics beyond the Standard Model. One of the important predictions of the model is the existence of new heavy gauge bosons, where they acquire mass terms through the breaking of global symmetry necessarily imposed on the model. The determination of the masses are, hence, quite important to test the model. In this paper, the measurement accuracy of the heavy gauge bosons at ILC is eported.